(a) Field
The described technology relates generally to a frame transmitting method and apparatus and a frame receiving method and apparatus. More particularly, the described technology relates generally to a frame transmitting method and apparatus and a frame receiving method and apparatus in a wireless local area network (WLAN).
(b) Description of the Related Art
In a wireless communication network such as the WLAN, each device occupies resources using a contention-based access scheme and transmits a signal. The WLAN device uses a carrier sense multiple access (CSMA) protocol to avoid collisions. In the CSMA protocol, the WLAN device detects energy on a channel and transmits the signal only when the channel is not being used. If the detected energy is above a clear channel assessment (CCA) level, the WLAN device deems that the channel is busy and defers the transmission attempt.
The CCA level is fixed in the conventional WLAN. For example, the CCA level for 20 MHz transmission is −62 dBm in the conventional IEEE standard 802.11n.
A dynamic CCA scheme where the CCA level is not fixed but can be changed has been developed in the IEEE 802.11ah task group (IEEE 802.11ah). In the dynamic CCA scheme, after identifying a basic service set (BSS) of the received packet, the WLAN device decreases the CCA level to protect the packet when the packet belongs to its own BSS and increases the CCA level to enhance the throughput when the packet belongs to another BSS. However, since the IEEE 802.11ah task group targets the WLAN operating at 1 GHz, the dynamic CCA scheme developed by the IEEE 802.11ah task group can be used only when devices existing in the BSS support IEEE standard 802.11ah.
Recently, the IEEE 802.11ax task group has been developing a high efficiency wireless WLAN (HEW) for enhancing the system throughput in high density scenarios. In the high density scenarios, devices of the previous version (for example, IEEE standard 802.11a, IEEE standard 802.11g, IEEE standard 802.11n, or IEEE standard 802.11ac) as well as HEW devices may coexist in the BSS. Therefore, if the dynamic CCA scheme developed by IEEE 802.11ah task group is applied to the HEW, the HEW devices can use the dynamic CCA scheme only on packets transmitted as HEW formats but cannot use the dynamic CCA scheme on packets transmitted as previous formats (for example, formats based on IEEE standard 802.11a, IEEE standard 802.11g, IEEE standard 802.11n, or IEEE standard 802.11ac).
Further, the devices of the previous version can identify the BSS of packets that are being received. In this case, the devices of the previous version can identify the BSS by interpreting a medium access control (MAC) frame on a MAC level. However, errors can occur when the device interprets the MAC frame.